Tank Volume Calculator

How tank volume is calculated

For a rectangular tank the formula is straightforward: Volume = Length × Width × Height. All three dimensions must be in the same unit. The result in cubic centimetres is divided by 1,000 to give litres.

A cylindrical tank uses the circle area formula: Volume = π × r² × Height, where r is the radius (half the diameter). An L-shaped tank is treated as two joined rectangles: Volume = (Length₁ × Width₁ + Length₂ × Width₂) × Height.

The calculator accepts measurements in centimetres or inches and converts automatically. One litre equals 1,000 cm³, one US gallon equals approximately 3,785 cm³, and one UK gallon equals approximately 4,546 cm³.

Choosing the right shape

Rectangular tanks are the most common for home water storage, aquariums, and IBC containers. Cylindrical tanks are typical for fuel, rainwater butts, and industrial storage. L-shaped profiles appear in custom aquarium installations and split-level pond setups.

For round or oval tanks that are not perfectly cylindrical, measure the widest diameter and use the cylindrical formula as an estimate, then adjust downward if the vessel tapers significantly.

Weight of water in a full tank

One litre of fresh water weighs approximately 1 kg. A 500-litre tank therefore holds roughly 500 kg of water. This is an important load consideration for structural floors, mobile platforms, and vehicle water tanks.

Salt water is approximately 2.5% denser than fresh water, so a 500-litre marine aquarium holds around 512 kg of water alone, before accounting for substrate, rock, and glass.